Device having reflective and transmissive properties

ABSTRACT

A device which simultaneously maximizes light reflectivity from one side of the device while maximizing light transmissivity from the opposite side of the device. The device is configured with distinct regions of transparency and reflectivity including a plurality of reflective structures. The structures are generally smaller towards a light transmitting side of the device and larger towards a light reflective side of the device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/990,102 filed on Nov. 16, 2004 now U.S. Pat. No. 6,919,981, which isa continuation of U.S. application Ser. No. 10/282,702 filed on Oct. 29,2002 now U.S. Pat. No. 6,819,465, which is a continuation of U.S.application Ser. No. 09/491,450 filed Jan. 26, 2000, now U.S. Pat. No.6,473,220, which is incorporated by reference herein, which is acontinuation-in-part of U.S. application Ser. No. 09/234,522 filed Jan.21, 1999, now abandoned, which claims the benefit of ProvisionalApplication No. 60/072,202 filed Jan. 22, 1998.

BACKGROUND

The prior art for non-emissive displays, particularly liquid crystaldisplays, include either reflective displays or surface light source(transmissive) displays, commonly denoted backlit displays. Theconventional reflective display which uses a reflective film as thebottom layer to redirect ambient light back through the display elementshas a composition as illustrated in FIG. 1. In this drawing ambientlight 10 (sunlight, artificial light—such as office lighting—or from alight source 11 attached to the top of the unit) enters the displayunit, passes through the various layers of the unit, 6 polarizers, 7glass plates (which may include color filters, common electrodes, TFTmatrix, or other components), and 8 liquid crystal suspension, and isredirected from the reflective film 9 back through the various layers toproduce an image. This method of creating an image with availableambient light is limited by the available light. This method is not aneffective means for producing high quality graphic images and severelylimits the quality of color images in a variety of conditions. Theconventional backlit (transmissive) display has a composition asillustrated in FIG. 2. In this drawing, light is produced with abacklight assembly 12 and directed as light ray 13, through the variouslayers, such as 6 polarizers, 7 glass plates (which may include colorfilters, common electrodes, TFT matrix, or other components), and 8liquid crystal suspension, to produce an image.

Previous attempts to use simultaneously the ambient light and abacklight have resulted in applications that compromise both thetransmissive qualities and the reflective qualities of the display.Hochstrate, in U.S. Pat. No. 4,196,973 teaches the use of a transflectorfor this purpose. Weber, in U.S. Pat. No. 5,686,979, col. 2, teaches thelimitations of the transflector for this purpose and alternativelyproposes a switchable window that at one time is wholly transmissive andat another time is wholly reflective.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (prior art) is a diagram showing the operation of a conventionalreflective display.

FIG. 2 (prior art) is a diagram showing the operation of a conventionalbacklight display.

FIG. 3 is a diagram showing one example of a backlight embodimentincorporating a device having reflective and transmissive properties.

FIG. 4 is a diagram showing one example of a solar panel embodimentincorporating a device having reflective and transmissive properties.

FIG. 5 is a diagram showing one embodiment of a non-emissive displayincorporating a device having reflective and transmissive properties.

FIG. 6 is a diagram showing another embodiment incorporating a devicehaving reflective and transmissive properties.

FIG. 7 is a diagram showing a cross section of another embodimentincorporating a device having re and associated light paths.

FIG. 8A shows a perspective view of one embodiment of a device havingreflective and transmissive properties.

FIG. 8B shows a bottom view of FIG. 8A.

FIG. 8C shows another embodiment of a bottom view of FIG. 8A.

REFERENCE NUMERALS IN FIGS. 1–7

-   6 polarizers-   7 glass plates-   8 liquid crystal suspension-   9 reflective film-   10 ambient light from sun or room-   10A light ray striking absorber directly-   10B light ray strikes absorber directly, is reflected off absorber,    is reflected off base of reflective structure back to absorber, etc.-   10C light ray strikes side of reflective structure and is directed    to absorber, is reflected off absorber, is reflected by base of    reflective structure back to absorber, etc.-   11 controllable source of light from exterior of display-   12 backlight assembly-   13 light ray from backlight assembly-   14 transparent material of the device-   15 reflective material of the device-   16 remainder of the non-emissive display system-   17 base of the reflective structure-   18 spacing between reflective structures at the base-   19 thickness of the device-   20 height of the reflecting structure from base to apex-   21 the number of reflecting structures per pel (picture element of    display)-   22 device in cross-section-   23 the sun-   24 absorbing material in a solar collector-   31 transparent material-   32 reflective/refractive shapes-   33 a reflective material-   34 collimator-   35 light ray-   36 light ray-   37 light ray-   41 boundary edge of the device-   42 body of the device-   43 structures-   44 light ray-   45 light ray-   46 light ray-   47 light ray-   48 light ray-   49 light ray

DETAILED DESCRIPTION OF THE INVENTION

Generally, the device described herein, which will be described ingreater detail below, has reflective and transmissive properties suchthat R+T>1. The device may be used in any and all applications wherethere is a requirement in which reflectivity of incident energy or light(visible through infrared) coming from a first direction andtransmissivity of energy or light coming from the opposite direction aresimultaneously enhanced. That is, the sum of the reflectivity from thefirst direction and the transmissivity from the opposite directionexceeds 1.0 as shown in one embodiment above. The device may be referredto as a multiflector or a transflector that is capable of simultaneouslytransmitting and reflecting light such that R+T>1.

One application area for the device is for solar collection in whichtransmission of light would be maximized (reflectivity minimized) in thedirection facing the sun and reflectivity maximized (transmissivityminimized) in the direction facing the collector. The device shouldincrease the level of retained energy in such devices. Additionally, thedevice could be used as part of a heating, cooling and/or powergenerating system in which solar energy is utilized for some or all ofthe power generation. The device should increase the efficiency of solarcollectors and will thus reduce the use of fossil fuels.

The term “light”, as used herein, encompasses electromagnetic radiationwith wavelengths corresponding to visible through infrared. The device,however, can be formed to be applicable to any electromagnetic radiationthat is capable of being reflected or refracted, subject to the abilityto create structures of a size and a material to do so. Specifically,embodiments of the device can find applicability in the radio, radar,microwave, infrared, visible, ultraviolet, x-ray and gamma forms ofradiation.

Another application area includes use with any non-emissive displaytechnology—such as electrochromic, ferroelectric, ferromagnetic,electromagnetic, and liquid crystal—where it is desired to use bothexternally generated (ambient) light and internally generated(artificial) light. The device may be a replacement for thetransflective/reflective/transmissive element of the non-emissivedisplays, where the replaced element is either independent of orintegral to the internally generated light (backlight system). Use ofthis device should allow brightness contributions simultaneously fromartificial light and ambient light such that systems will see asignificant decrease in power usage. In system where a battery is usedfor some or all of the power supply, battery life can be increased.

Another application area includes building materials in which the devicecan be used to direct light from a light source (such as a window orskylight) while at the same time reflecting ambient light within abuilding or structure. It will be appreciated that other applicationsexist where light is desired to be controlled or required.

In one embodiment, the device may take the form of a film that may bedesigned as an integral element of a system or product in which it is apart. The film includes a transparent body containing a set ofindentations, or discrete shapes, which may be filled with reflectivematerial(s). The indentations may be configured to have a variety ofcross-section shapes such as a triangle or other polygon which may bearranged in a variety of patterns. The indentations may be replaced by aseries of discrete objects such as pyramids, cones, or any polyhedron,and likewise may be arranged in a variety of patterns. The discretefaces of the indentations or objects may be planar, concave, convex, orpitted such that light reflecting from any face may be controlled. Thepreferred material for filling the indentations is a material with highreflectivity such as aluminum or silver, but may be a composite paste, acomposite material, or multiple materials with different refractiveindices or reflective qualities. In one embodiment, the reflectivematerial is embedded in the transparent material such that the base ofeach shape is approximately parallel to and coincident with, or slightlyrecessed from the transparent material. The indentations, or discreteobjects, may be repeated in parallel and spaced across the area of thefilm. The indentations, or discrete objects, may be arranged in varyingshapes, heights, angles, or spacings before a pattern is repeated, ormay be randomly distributed.

In FIG. 3, let 14 represent the transparent material, 15 represent lightdirecting/funneling structures and/or microstructures such as reflectiveindentations or objects, 12 represent the backlight assembly, and 16represent the remainder of the non-emissive display system and thedirection from which the display is viewed. Let:

17 = r = half width of base of the groove, or object 2r = base ofgroove, or object f = multiple of the half width of base of the groove18 = fr = spacing between indentations 19 = Th = film thickness (basedon the height of the groove, or object, and is determined by the natureof the transparent material) K = multiple of the half-width of base ofthe groove 20 = Kr = height of groove, or object 21 = M = number ofindentations per pel (picture element) defined here as the smallestcontrollable area of the display Also let R_(M2) = reflectance of thereflective material to normally incident light 22 represent oneembodiment of the film

Mirror-like and funnel effects can be accomplished by using acombination of appropriate (1) shaping of the material comprising thefilm and (2) choice of materials with either different reflectivities,indices of refraction, composites, or a combination of these. The lightdirecting/funneling structures and/or microstructures 15 may be formedfrom a variety of structures which may include, but are not limited toindentations (intersecting or not), cones or other conic sections,multi-sided structures (regular or not) such as pyramids ortetrahedrons, all structures of the same or different sizes generallyvaried periodically and in which the reflectance, transmittance, andabsorption of the film might have different values. This enables theachievement of high reflectivity and low transmissivity through the filmin one direction and high transmissivity and low reflectivity in theother direction.

-   R₁=reflectivity from one side-   T₁=transmissivity from one side-   A₁=absorptivity from one side-   R₂=reflectivity from the other side-   T₂=transmissivity from the other side-   A₂=absorptive from the other side-   From the conservation of energy: R₁+T₁+A₁=1 and R₂+T₂+A₂=1. In the    prior art of transflectors, R=R₁=R₂; T=T₁=T₂; and A=A₁=A₂. It    follows that in the p designs, R+T=1 when A=0. Even where prior art    claims to overcome the limit of transflectors and where the    disclosed transflector is meant to channel or direct light, no    overall transmitance or reflectance is shown so that any possible    gain cannot be determined and is not apparent.

In this art, the value of the reflectance on one side of the film issignificantly decoupled from the value of the reflectance on the otherside, and the value of the transmissivity on one side is significantlydecoupled from the value of the transmissivity on the other side. Thisnewly disclosed film allows R₁≠R₂, T₁≠T₂, and A₁≠A₂. A specificembodiment will be shown below in which T₁, R₂, A₁, and A₂ are small. Itfollows that R₁+T₂>1. This disclosed film multiplies the transflectingeffect. In the theoretical limit, for this non-emissive version of thefilm, T₁=R₂=A₁=A₂=0. Then R₁+T₂=2.

The first embodiment of the film is related to uses in which light is tobe directed without regard to dispersion upon transmission, inparticular for use in solar collectors or any device in which radiatedlight is to be directed or collected as illustrated in FIG. 4. In thisdrawing light from the sun 23 enters the transparent material 14 aslight ray 10A and is transmitted directly to an absorbing material 24.Light ray 10B passes through the transparent material 14 and ispartially reflected by the absorbing material 24. Light ray 10C passesthrough the transparent material 14 and is redirected by the reflectingstructure 15 to the absorbing material 24, is partially reflected by theabsorbing material 24. The film material will be highly opticallytransmissive to visible, ultraviolet, and/or near infrared light betweenabout 300–2,500 nanometers, stable to ultraviolet light, impervious tomoisture, non-hygroscopic, scratch resistant, and easy to keep clean,with an appropriately chosen refractive index to match the otherelements of the system in which it is a part. If adhesive is used toadhere the film 22 to another substrate, the adhesive should be highlyoptically transmissive to light between about 300–2,500 nanometers andstable to ultraviolet light. In the first embodiment, the design is formaximum sum of transmissivity and reflectivity. Then maximum sunlightwill be collected and retained within the specific device in which thefilm is a part. Therefore, for this embodiment, let R_(M2)=1.00; aperfectly reflecting material. Let f=0.1, the practical limit formanufacturability of the indentations. Choose values for r and f largeenough to avoid diffraction and interference effects. For example,choose r=200Φ so that the spacing between adjacent indentations at thebase is 20Φ, well above the longest wavelength of visible light. For asolar collector where multiple reflections during transmission areinsignificant as long as perfectly reflecting material is used,R₁=2/(2+f)=0.952 and T₂=1.000. Thus, R₁+T₂=1.952, near the theoreti of2.000. Thus, virtually all light energy entering the system will betrapped.

A second embodiment of the device is related to use with a non-emissivedisplay system, such as liquid crystal displays, or other devices inwhich light is directed for the purpose of creating an image. Onceagain, the device may take the form of a film 22. In this embodiment,the film 22 may be inserted between the backlight assembly and theremainder of the display system, may be a component of the backlightassembly, or may be attached to a component of the remainder of thedisplay. One example of an artificial light source in this case wouldinclude a means of collimating light such that a majority of lightemerges perpendicular to the film 22. The highly transmissive side ofthe film 22 faces the backlight system and the highly reflective sidefaces the viewer. The film will cover the full area of the display. Theindentations or objects may be arranged at any angle to the edge of thedisplay, from parallel to oblique.

One embodiment of a non-emissive display system including an embodimentof the film 22 is illustrated in FIG. 5. In this drawing, ambient light10 will pass through the various layers 6 polarizers, 7 glass plates(which may include color filters, common electrodes, TFT matrix, orother components), and 8 liquid crystal suspension and will beredirected by the reflective elements of the film 22, back through thevarious layers 6 through 8, while at the same time artificial light rays13 generated from backlight assembly 12 will pass through thetransparent elements of the film 22 which may be attached to adjacentelements such as backlight assembly 12 or be installed as a separatelayer in the display system. It will be appreciated that different typesof layers may be used rather than layers 6–8, additional layers may beincluded for desired effects, and the positioning of the film 22 orother layers may be changed.

Let

-   W_(T)=width of the display-   m=number of indentations per pel (picture element) defined here as    the smallest controllable area of the display-   F_(w)=format of display in horizontal direction (number of distinct    elements, where each element has a red, green, and blue pel)-   Then r=W_(T)/[3 F_(W)m (2+f)] for a color liquid crystal display. To    illustrate one example method of design, let W_(T)=246 mm and    F_(W)=800 represent the typical values for a vintage 1996/97 color    liquid crystal display design. Also, let m=3 to eliminate the    necessity of alignment of the film 22 with the pels of the display    during the display assembly process. Additionally, m may be    increased or decreased as necessary to eliminate visible    non-uniformities in the light distribution, such as banding, which    may be created by the film 22.

For the designs shown for the second embodiment, let f=0.5. Thisminimizes the redirection of light, preserving the original direction ofthe transmitted light. For this value of f, 20% of parallel light fromthe backlight system will be transmitted without reflection, 40% will betransmitted with one redirection from the reflecting indentations orobjects, and 40% will be transmitted after two redirections from thereflecting indentations or objects. In this instance r can be calculatedusing the equation r=W_(T)/[3 F_(W) m (2+f)] to be 13.7Φ with a spacingfr (spacing between indentations) of 6.90Φ. The reflectance R₁ andtransmittance T₂ can be computed if R_(M2) (normal reflectance of thematerial) is known. Note two design examples:

-   1. Let R_(M2)=1, then R₁=2/(2+f)=0.8. and T₂=1.0, resulting in R₁+T    ₂=1.8.    2. Let R_(M2)=0.86, then R₁=2R_(M2)/(2+f)=0.688. and T₂=0.840,    resulting in R₁+T₂=1.528.    Both designs show an improvement available from use of the film 22.

Another embodiment is shown in FIG. 6. Let 31 represent the transparentmaterial (body of the device 60), 32 represent the reflective/refractiveshapes, 33 represent a reflective material (where no fill, gas, vacuum,or a change of indices of refraction are used to create structures), and34 represents a collimating element attached to the device 60. Light ray35 strikes the base of a shape 32 and is redirected away from the device60 (reflected). Light ray 36 enters the device 60 from a transmissiveenergy source (not shown), passes through the collimator 34 withoutredirection, passes through the transparent body 31 of the device 60without striking any shaped structures 32 and exits the reflecting sideof the device 60 without redirection. Light ray 37 enters the collimatorfrom a transmissive energy source (not shown) at an incident angle forexample greater than 10 degrees, and is redirected by the collimator 34to less than 10 degrees. Light ray 37 enters the transparent body 31 ofthe device 60 and passes through without being redirected.

FIG. 7 represents a cross section of another embodiment of the device70, where 41 represents the boundary edge of the device 70. One or morestructures 42 extend into the device 70 a percentage of the total device70 thickness. As used in this patent, the term “structure” refers to theshape of the device refracting or reflecting light. The structure may bea physically separate item mounted on or in the light transmittivematerial, it may be formed or represent a groove or indentation that hasbeen cut into the light transmissive material, or it may be the endresult of treatment of portions of the light transmissive material suchthat a shape having a different index of refraction is formed. Where thetransmissive material is a gas or vacuum, as may be found in solarapplications, the structure is mounted “in” the material by means of agrid, wire, filament or other such device, with the grid representing asurface of the transflector.

Let the apex 43 (tip) of structure 42 have an angle of 4 degrees.Additionally, let the apex 43 of structure 42 face one light source (notshown) while the base of the structure 42 faces another light source(not shown). Light ray 44 enters the device 70 perpendicular to theplane of the device 70 and passes through the device 70 without strikinga shaped structure 42 and exits the device 70 without redirection. Lightray 45 enters the device 70 perpendicular to the plane of the device 70and strikes the midpoint of a structure 42 and is minimally redirected(4 degrees relative to perpendicular to the plane of the device 70) suchthat it exits the device 70 without striking an adjacent structure 42.Light ray 46 enters the device 70 perpendicular to the plane of device70 and strikes a structure 42 near the apex 43 (tip) and is minimallyredirected (4 degrees relative to perpendicular to the plane of thedevice 70) such that it strikes an adjacent structure near the base ofthe structure (16.6% of the height of the structure) and is againminimally redirected (as above) such that the total redirection of lightray 46 is 8 degrees from the perpendicular to the plane of the device 70upon exiting the device 70. Light ray 47 enters the device 70 at anangle greater than 10 degrees of perpendicular to the plane of thedevice 70 and strikes a structure 42 above the midpoint and is minimallyredirected (4 degrees relative to perpendicular to the plane of thedevice 70). Due to the increased angle of entry of light ray 47,multiple redirections occur before light ray 47 exits the device 70. Inthis example, seven redirections are necessary for light ray 47 to exitthe device 70—the cumulative redirection is 28 degrees. Light ray 48 isreflected by a structure 42 at an angle equal to the angle of incidence.Light ray 49 enters the device 70 at a steep angle relative to theperpendicular to the plane and strikes a structure 42 near the apex(tip), due to the cumulative redirection light ray 49 cannot exit theopposite side of the device 70.

The multiflector shown in FIG. 7 is configured with structures 42 at anaspect ratio of 14.3, a spacing between structures 42 of 25% of the basewidth, and structures evenly spaced across the body of the device 70.Such a device 70 will produce a transmissivity of 94% of light raysentering the device 70 perpendicular to the plane from the side closestto the apex (tip) of structures 43 (transmissive side). The device 70described above will provide the additional benefit of reflecting 76% oflight striking the device 70 from the opposite direction. In thisexample, 20% of light entering from the transmissive side will passthrough the device 70 without redirection, 40% will pass through with asingle redirection (4 degrees relative to perpendicular to the plane ofthe device 70) and 40% of the light will have two redirections (8degrees relative to perpendicular to the plane of the device 70). Thisexample provides an R+T of 1.70. The combination of aspect-ratio andspacing of structures described above are intended to illustrate theeffects of one configuration of the device and are not intended to bethe only configuration that may be designed.

Another embodiment of the device is related to uses in which light is tobe directed or focused upon transmission, in particular for use inbuilding materials where light from the sun is used to illuminate aninterior area or augment artificial lighting. In this embodiment theindentations, or objects, may be angled such that the base of theindentation, or object is not parallel or coincident with the boundaryof the transparent material. This embodiment will allow the light to bedirected at a given angle to the transparent material independent of theangle of the light source.

One embodiment of the device may be stated as being a transflectorhaving means for reflecting of light impingent thereon from a firstdirection, and having means for transmitting of light arriving from adirection opposing to said first direction wherein the sum of thepercent of light being reflected relative to the light coming from thefirst direction, and the percent of light being transmitted relative tothe amount of light coming from the opposing direction, is greater than100 percent.

Another embodiment of the multiflector may be stated as a lighttransmitting material capable of transmitting light in a first andsecond direction, having a first surface, said first surface havingreflecting means for reflecting a percentage but not all of the lightstriking said first surface from said first direction, and having one ormore reflecting structures associated with said reflector means, saidstructures having sidewalls extending from said first surface, saidsidewalls being at an angle sufficient to reflect light striking saidstructure from said second direction through said first surface suchthat a percentage of light from said second direction passes throughsaid first surface, wherein the sum of the percent of light beingreflected relative to the light coming from the first direction, and thepercent of light being transmitted relative to the amount of lightcoming from said second direction is greater than 100 percent.

The device is independent of any specific system, but will typically beincluded as one of several elements incorporated within a system. Thedevice will provide optimized reflection of energy in one directionwhile simultaneously optimizing the transmission of energy in theopposite direction. This is accomplished, for example, by utilizinghigh-aspect ratio structures embedded, embossed, or by other meanscreated in the body of the device or deposited or suspended in thetransmissive device. In general, by increasing the surface area of thereflecting/refracting structures in a direction from the apex of thestructure to the base of the structure, the amount of energy that canreflected in one direction can be decoupled from the amount of energytransmitted in the opposite direction. In other words, the reflectingstructures are formed and oriented such that they have a smallercross-sectional area towards the transmissive side of the device and alarger cross-sectional area towards the reflective side.

Illustrated in FIG. 8A is a partial cutout perspective view of amultiflector 800 which has a light receiving side 805 and a lightreflecting underside 810. The example shows three lightreflecting/refracting structures 815 a, 815 b, 815 c which arepositioned side by side but spaced apart a selected dimension asdescribed above. A view from the under side 810 is shown in FIG. 8B. Inthis embodiment, the reflective structures 815 a–c have a shape thatdecrease in size towards the transmissive side 805 and increase in sizetowards the reflective underside 810. Although a triangular shape isshown, any shape may be used which is generally smaller at the lighttransmissive side 805 than at the light reflective side 810. It will beappreciated that the sidewalls of the reflective structure 815 a–c mayor may not be smooth based on a desired effect and manufacturingtolerances. Each structure 815 a–c has an elongated body which canextend the length of the multiflector 800 or a sub-portion thereof. Forexample, FIG. 8C shows an embodiment where the reflective structures 815are formed or deposited within the transmissive material 820 as smallerunits uniformly distributed and oriented in the multiflector 800. Eachstructure 815 is shown having a square base adjacent the reflective side810, however, any desired shape may be used as the base and thestructures 815 may be oriented in any desired pattern including a randompattern. It will be appreciated that dimensions in all illustrativefigures are not to scale.

The device can be placed in conjunction with other devices to produceadditional effects. For example, a collimating device may be integratedwith the device to form a single device, attached to the device, orincorporated into another component of a system to which the device isattached, such that the collimating device is proximal to thetransmitting side of the device and between the device and thetransmissive light source. The collimating device accepts incomingenergy waves distributed over a broad angle and redirects the energywaves to emerge at an angle less than some specified angle as measuredfrom the normal to the surface of the device. The use of a collimatingdevice ensures that virtually all energy entering the device from thetransmissive side will be constrained within an arc of about 10° ofperpendicular to the plane of the device. Of course, a collimator withother light controlling properties can be used. Constraining transmittedenergy in this manner will improve the performance of the device, but isnot a requirement for the device to produce beneficial effects.

The determining factors for configuring the device are the aspect ratioof the reflecting/refracting shaped structures, spacing betweenstructures, and materials used to construct the device. These factorsdetermine (1) the allowable incident angle of the energy entering thedevice from one direction (transmissive), (2) the proportion of energytransmitted from that direction, (3) the proportion of energy reflectedby the opposite side of the device, (4) the distribution of energyemerging from the device, (5) the percentage of energy lost to internalabsorption or scattering. Aspect ratio (the ratio of height to base) ofthe reflecting/refracting shapes determines the relationship between thespecific angle at which the transmitted energy enters the device and theangle at which the transmitted energy emerges from the device. Thespacing between the shaped structures determines the proportion ofenergy reflected by the device (from the reflective side) and thedistribution of transmitted energy (from the transmissive side). Byincreasing the spacing between the shaped structures, a smallerproportion of energy is redirected from the transmissive side whilereflection of energy from the opposite direction is reduced. Conversely,by decreasing the spacing between the shaped structures, a greaterproportion of the transmitted energy will be redirected while a largerproportion of the energy from the opposite direction will be reflected.The general relationship between the aspect ratio of height to base forthe reflecting/refracting structures and the spacing between structuresis illustrated in the following examples:

EXAMPLE 1:

A single structure is triangular in cross section and extends along thefull length of the device from one side to the other. The abovestructure is repeated at regular intervals such that one side of theentire body of the device is covered with the bases of alternatingtriangular rows and spaces in-between. If the specific applicationrequirement for the device calls for approximately 66.6% of the energyfrom one side (the reflecting side) is to be reflected and thetransmitted energy from the opposite side is restricted to emerge about5°, than the aspect ratio must be a minimum of 11.5:1. The spacingbetween the shaped structures in this example will be approximately halfthe dimension of the base of a shaped structure. In this example the sumof potentially useful reflected energy from one side R plus the sum ofpotentially useful transmitted energy from the opposite side T isapproximately 1.66 (R+T=1.66). This can be restated as 66.6% of theenergy entering the device from the reflective side is reflected and100% of energy entering the device from the transmissive side istransmitted (R=66.6% and T=100% so that R+T=166%).

EXAMPLE 2:

Assume that the shaped structures are the same as in example 1 and thatthe specific application requirements call for maximizing the amount oftransmitted energy independent of any specific angle of emergence. Alsoassume that the energy entering the device from the transmissive side isuniformly collimated within about 10° of perpendicular to the plane ofthe device.

In this application the requirements are for reflection of about 80% ofthe energy in one direction (the reflecting side) and for transmissionof more than 95% of the energy from the opposite side (the transmittingside). A device having structures with an aspect ratio of 15:1 will beapproximately 96.8% transmissive, assuming a perfectly reflectingmaterial for the structures. The spacing between the structures is aboutone-fourth the dimension of the shaped structures. In this example thesum of potentially useful reflected energy from one side R plus the sumof potentially useful transmitted energy from the opposite side T isapproximately 1.77 (R+T=1.77).

Additionally, the device can be configured to specifically control thedistribution of both reflected and transmitted energy. As an example,such a configuration may be useful in a display application to improveviewing angle.

A light ray striking a triangular row of structures near the tip willhave the most number of redirections before possibly exiting the device.By using basic geometry and a rudimentary understanding of geometricoptics, one skilled in the art can calculate what aspect ratio and widthbetween structures is necessary to preferably redirect light strikingnear the tip no more than twice before exiting. A geometric plot of thelight ray path can be used to derive the relationships between thevarious parameters, including the constraints of the system. The heightof the structure will be determined by several factors, among which isthe thickness of the transparent material. If the requirement of aspecific application is to transmit light through the transflectorwithin 10 degrees of perpendicular, then assuming a height, one can plotor calculate the apex angle. The apex angle and the height will give theaspect ratio and thus the width of the base of the structure.

In non-emissive displays, the device should not exceed 100 milsthickness. The body of the device should have a transmissiveco-efficient of >97%. The apex (tip) of each of the shapes penetratesinto the body of the device a percentage of the total thickness between10%–100%. Each shape will have a fixed apex angle of between 2.6°–9.5°,with an altitude to base ratio of between 6:1–22:1. In anotherembodiment, the shape will have a fixed apex angle of between 3.0°–7.0°,with an altitude to base ratio of between 8:1–18:1. In eitherembodiment, the altitude to base ratio may be as low as 4:1. Thisresults in the walls of the structure being at an angle relative to thebase of between about 83 degrees to less than 90 degrees. The base ofthe shape is parallel to a surface of the device and has a base width ofbetween 2.0Φ–200.0Φ (Φ=microns). In another embodiment, the base widthmay be between 2.0Φ–50.0Φ. Whether the shape is created with fillmaterial or through an optical process, the base of each structure needsto be reflective. This can be achieved either through a fill process,through a deposition/photoresist process, or other methods such as theuse of overlays. The triangular row structures are periodically repeatedwith a fixed spacing between the apex of each triangle of between3.0Φ–300.0Φ and the spacing between the base of each adjacent isoscelestriangle is between 1.0Φ–100.0Φ. In another embodiment, the spacingbetween the apex may be between 3.0Φ–70.0Φ and the spacing between thebases may be between 1.0Φ–20.0Φ. In the preferred embodiment, acollimating device is attached to the device adjacent to thetransmitting side of the Multiflector device. The dimensions describedin the preferred embodiment should not be interpreted as limitationssince other applications may require, or allow, variations on the abovespecifications.

In the preferred embodiment, the cross section of a single shape istriangular and extends from one edge of the device to the opposite edgeto form a single row and is oriented in the transparent material (bodyof the device) such that the base of the triangle is parallel to andcoincident with, or slightly recessed from, the plane of one surface ofthe body of the device (the reflective side). In the preferredembodiment, said triangular row is repeated in parallel and evenlyspaced across the entire area of the device forming a striped pattern ofshapes and spaces. In other embodiments the triangular-shaped rows maybe replaced by discrete objects such as pyramids, cones, or anypolyhedron, and likewise may be arranged in a variety of patterns toachieve specific effects. In other embodiments, the discrete shapes, asdescribed above, may be arranged in varying shapes, heights, angles, orspacing. In the preferred embodiment, the discrete faces of eachtriangular row are planar. In other embodiments one or more of thediscrete faces of the row, or discrete shapes, may be concave, convex,and/or pitted. Additionally, micro-shapes (such as pyramids or cones)may be deposited on the flattened base of each structure to furthercontrol the direction of reflected energy.

In one embodiment, the material for the transparent “body” of the devicewill have specific properties that minimize absorption and redirectionof energy—such as internal scattering. In addition, the material for thebody of the device will require specific properties necessary foretching, molding, or other processes that alter the body of the device.Examples of suitable materials are polymers such as polycarbonate andPMMA (polymethylmethacrylate). Where etching, molding, or embossing isused to create a series of indentations in the body of the device, fillmaterial such as a highly reflective metal may be used. Additionally,clear material such as a polymer, or no material (gas, air, or vacuum)may be used to fill the indentations. Where clear material or nomaterial is used to fill the indentations, the material chosen for thebody of the device should have a higher index of refraction than thefill. The minimum difference in index of refraction between the fill andthe body of the device is estimated to be 0.01. In the preferredembodiment, indices of refraction are the same for each shape across thebody of the device. For purposes of the present discussion, the termreflection, when discussing light striking the body of the structure,also includes refraction where the difference in the index of refractionof the materials, along with the angle of incidence, results insubstantial or near total reflection of the light striking thestructure.

Where the indentations are filled with a reflective material, a singlematerial, or composite material, may be used to create the abovementioned triangular rows. The fill material for the reflective shapeswill be optimized to minimize absorption and have highly reflectiveproperties for the controlled redirection of energy. Examples ofsuitable materials are aluminum or silver, with a reflectivity of 95% orgreater, but may be a composite paste, a composite material, or hybridmaterials with different refractive indices or reflective qualities.

As described above, the reflective material may be coated on thetransparent body, be part of the fill for grooves in the body, or be thebase of the refracting structure physically separate from but attachedto the transparent body.

A second method of creating an embodiment of the device may includeproducing the above-described triangular rows in a photosensitivetransparent material. The desired shapes are produced by changing theindex of refraction in specific areas of the body of the device. In thisembodiment, a thin layer of reflective material, such as aluminum, isdeposited on one side of the device, adjacent to the base of thetriangular rows (reflective side). Regions of the deposition are removedcorresponding to the spaces between triangular rows, creating a stripedpattern across the device. Utilizing an optical process to change theindex of refraction of specific areas of the device will requirephotosensitive materials that exhibit favorable optical and mechanicalproperties. In addition to a sufficient photo-induced refractive indexchange, a suitable set of “writing” wavelengths (typically in theultraviolet), optical transparency, thin film formability, andmechanical behavior can be design considerations. Such materials may beorganic polymers that have optimized mechanical behavior, ororganic-inorganic hybrids that combine the chemical versatility oforganic polymers, i.e. polysilanes, polygermanes, and/or their sol-gelhybrids.

In other embodiments related to utilizing a photosensitive transparentmaterial, discrete shapes may be arranged in varying shapes, heights,angles, or spacing and one or more of the discrete faces of a shape,including the triangular rows, may be concave, convex, and/or pitted.Additionally, micro-shapes (such as pyramids or cones) may be depositedon one side of the body of the device directly over the base of eachstructure, either as part of a deposition process, described above, oras an independent process, to further control the direction of reflectedenergy. In other embodiments, the indices of refraction may be differentfor each discrete shape such that various alternating patterns areproduced across the body of the device to achieve specific effects. Inother embodiments, a combination of shapes created by filledindentations and altering the refractive index of a photosensitivematerial may be used to create various patterns across the body of thedevice.

Another method of creating the structures of the device is byfabrication of the structures from some suitable material that willmaintain integrity in the physical working environment, and suspendingthe structures by some suitable method. Suspension may be accomplishedby the use of wire or some type of filament that forms a grid, but willdepend on the specific application and will be apparent to one skilledin the art. This aspect is useful in solar applications, where the sizeof transflectors are not limited by the size requirements ofnon-emissive displays.

One of the more common methods of collecting solar radiation is by theuse of mirrors to reflect radiation from the sun onto a complex ofpipes. The pipe complex may include a first pipe carrying the liquid tobe heated, surrounded by a second pipe. The space between the two pipeswill typically be evacuated to decrease the amount of convection andconduction loss. By mounting the device structure within this spacebetween the pipes, the majority of solar radiation from the mirror willbe trapped and reflected back onto the pipe to be heated, thusincreasing overall efficiency. In most situations, the heated pipe willalso be emitting radiation, which will also be trapped and reflectedback. Thus solar radiation passes through the transflector, whileradiation not initially absorbed by the solar collector, combined withany radiation being emitted from the solar collector due to it'stemperature, is reflected back to the solar collector. In thisembodiment, the vacuum is the transparent material associated with thestructure.

In such solar applications, the height of the structure will only bedependent on the spacing between the pipes, and the base of thestructure may be large as compared to the use in non-emissive displays.The width of the base may be 3500Φ or larger, although the smaller sizestructures will also be applicable to this use. The multitude ofstructures will preferably be bent around at least a portion of the pipeto improve both the gathering and reflection of radiation.

While the present invention has been illustrated by the description ofembodiments thereof, and while the embodiments have been described inconsiderable detail, it is not the intention of the applicants torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the invention, in its broaderaspects, is not limited to the specific details, the representativeapparatus, and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of the applicant's general inventive concept.

1. A device having transmissive and reflective properties produced bythe process comprising the steps of: providing a transparentphotosensitive film; providing a reflective metal layer on a selectedregion of the surface of the photosensitive film, wherein the selectedregion is less than the complete surface of the photosensitive film anddefines a non-selected region; and changing the optical characteristicsof the photosensitive film in the non-selected region to alter the indexof refraction of the photosensitive film in the non-selected region tothereby form an altered refractive index area.
 2. The device of claim 1,wherein the selected region of the photosensitive film comprises anunaltered refractive index area.
 3. The device of claim 2, wherein thealtered refractive index structure has a higher index of refraction thanthe unaltered refractive index area.
 4. The device of claim 1, whereinthe selected region of the photosensitive film comprises a plurality ofunaltered refractive index areas.
 5. The device of claim 4, wherein theunaltered refractive index areas are triangular cross-section structureseach having a base, a height, and a pair of sidewalls each having anoutside surface, the base is associated with said reflective metallayer, each sidewall is at an angle relative to said base.
 6. The deviceof claim 1, wherein said reflective metal layer has a desiredreflectivity percentage.